Ignition system for jet engines and the like



o 1957 w. B. SMITS 2,810,866

IGNITION SYSTEM FOR JET ENGINES AND LIKE Filed June 17, 1954 INVENT OR W 5575 S V/ZE AITORNEY United States Patent IGNITION SYSTEM FOR JET ENGINES AND THE LH(E This invention relates to an ignition system for jet engines and the like, and more particularly to an ignition circuit which is suitable for use with low voltage spark plugs which operate on condenser charges and discharges.

Heretofore, in jet engine ignition installations, it has been the practice that there be provided only one or two spark plugs for a plurality of combustion chambers. In prior art ignition installations, the combustion chambers of jet engines have been connected by means of ducts or tubes and spark plugs have been installed in two spaced chambers. Initially, the fuel is fired in those chambers which are provided with spark plugs and the fuel in the remaining combustion chambers ignites by virtue of the flame passing through the connecting ducts.

The disadvantages in the prior art ignition systems described above are numerous. It is frequently the case that when flying at high altitudes or at high speeds, the burning fuel has been blown out, and it is exceedingly diflicult to relight the fuel. It has been necessary for the pilot to bring the plane to a lower altitude and lower speed before he is able to re-ignite the fuel.

The systems described above utilize the high voltage spark plugs of a well-known variety. It is, of course, impossible to provide each combustion chamber with a spark plug of the type referred to, since exceedingly high voltages would be required and the weight of the equipment required would render such a system impractical.

Another problem involved in the use of present day jet engines is that the ignited fuel within the combustion chambers frequently burns obliquely rather than in the center of the chamber. Such improper burning is caused if the fuel within an adjacent combustion chamber is not ignited whereby a lower pressure is created and the bruning fuel of the adjacent chamber is drawn towards the connecting duct. When the fuel in a combustion chamber burns obliquely, the walls of the chamber are subjected to tremendous heat, and the consequent difficulties are obvious.

The present invention overcomes all of the foregoing disadvantages by providing a novel circuit which utilizes low tension spark plugs. The spark plug used with this circuit is one such as disclosed in applicants Patent No. 2,125,035, issued July 26, 1938, for Electric Ignition System and Sparking Plug for Internal Combustion Engines. The essential feature of such spark plugs is that they employ relatively low voltages and provide a spark which, in effect, creeps across the surface of the plug. This creeping discharge is attained by providing a semiconductor between the electrodes of the plug. The advantages derived from this arrangement are numerous, one of the principal novel results being the obviation of cleaning the plugs. For purposes of the present invention, the spark plug described provides a spark which cannot be blown out since it does not rely upon the air as a conducting medium and therefore is not affected by variations in the atmospheric conditions.

,By utilizing spark plugs which require relatively low voltages such as described above, it is possible to provide Patented Oct. 22, 1957 an ignition system for jet engines, gas turbines or oil burners in which the spark plug can be inserted in each combustion chamber. In jet engine installations providing a spark plug in-each combustion chamber gives greater assurance of relighting' blown out chambers. Furthermore, the connecting ducts between adjacent combustion chambers can be omitted altogether if desired, thereby overcoming the difficulties encountered with oblique burning which have been pointed out hereinbefore. According to the present invention a low tension spark plug is provided in each of the combustion chambers of the jet engine. There is provided a rotor having three rings and three spaced contact members. There :are further provided three condensers which have brushes connected therewith engaging the rings on the rotor previously referred to. Inasmuch as there are three contact members and nine spark plugs, each spark plug is fired three times for each revolution of the rotor. By virtue of this arrangement, even if two of the condensers fail, the remaining condenser will serve to fire all of the spark plugs once during each revolution of the rotor. In this manner greater assurance of firing the spark plugs under any circumstances is provided.

The primary object of this invention is to provide an ignition system for jet engines and the like in which a spark plug is provided for each combustion chamber and in which each spark plug is fired sequentially by three independent condensers so that relighting blown out chambers may be more easily accomplished.

A further object of this invention is to provide an ignition system for jet engines and the like which utilizes low voltage spark plugs having a creeping discharge and in which condensers are used to fire the spark plugs.

Another object of this invention is to provide an ignition system in which a rotor is used to sequentially connect each of three condensers with successive spark plugs.

Other objects and many attendant advantages of this invention will become apparent in the light of this specification when considered in connection with the accompanying drawing.

In the drawing, individual condensers 16 are connected with the connectors 1, 2 and 3 which in turn contact brushes 4, 5 and 6. These brushes engage conducting rings 7, 8 and 9 respectively, which are mounted on a rotor. The conducting rings are provided with contact arms 10, 11 and 12, respectively, and these arms are adapted for engagement with contacts 13. Low voltage spark plugs of the type previously referred to are included in a circuit from contacts 13 to ground 15 and each spark plug is in a separate combustion chamber as shown generally in dot-dash lines around one spark plug.

It can be seen that each spark plug 14 is connected with each of the three condensers 16 during one revolution of the rotor. Thus, for each revolution of the rotor each spark plug is fired three times. It is obvious that the number of sparks desired may be adjusted by varying the rate of rotation of the rotor. It is further apparent that the present invention provides an ignition circuit in which, in effect, three independent circuits exist for firing each spark plug. The safety features of such an arrangement are evident.

Having thus described the invention is it obvious that numerous changes in design and construction of the same may be employed without departing from the essentials thereof. For example, it is obvious that the rotor may be provided with any suitable number of collecting rings and contact arms, and that by varying the number of rings and the rate of rotation of the rotor, the number of sparks per unit of time may be varied as desired. What is claimed as new and desired to be secured by Letters Patent is:

1. An ignition system for jet engines and the like in which a plurality of combustion chambers are provided, in combination, a spark plug of the creeping discharge type located in each of said combustion chambers, a plurality of ignition condensers, a rotor having a plurality of contact rings thereon, each of said contact rings being provided with a contact arm for connection with said spark plugs, and circuit means connecting each of said ignition condensers with one of said contact rings whereby each of said spark plugs is sequentially connected with each of said ignition condensers during one revolution of said rotor.

2. An ignition system for jet engines and the like acconnected with three contact arms so that each spark plug is fired three times for each revolution of the rotor.

References Cited in the file of this patent UNITED STATES PATENTS 1,459,252 Plumm June 19, 1923 1,507,307 Chryst Sept. 2, 1924 1,753,604 Hartzell Apr. 8, 1930 2,550,875 Smits May 1, 1951 FOREIGN PATENTS 697,953 Great Britain Oct. 7, 1953 

